Nonlinear low noise particle-in-cell simulations of electron temperature gradient driven turbulence

In this Letter, it is shown that global, nonlinear, particle-in-cell (PIC) simulations of electron temperature driven turbulence recover the same level of transport as flux-tube codes when the level of statistical noise, associated with the PIC discretization, is sufficiently small. An efficient measure of the signal-to-noise ratio, applicable to every PIC code, is introduced. This diagnostic provides a direct measure of the quality of PIC simulations and allows for the validation of analytical estimates of the numerical noise. Global simulations for values of rho(*)(e)< 1/450 (normalized electron gyroradius) show no evidence of a gyro-Bohm scaling. (c) 2007 American Institute of Physics.